Dynamo electric machines and stators for use in same

ABSTRACT

Dynamo electric machines and stators for use in such machines are provided. The stators comprise plates configured to be substantially flat and a plurality of spaced apart projections or teeth extending away from the plate and, together with the plate defining a plurality of slots therebetween. The stators comprise masses of metal particles. Using stators made from such metal particles provides enhanced machine efficiency, which is believed to be because of reduced eddy current effects in the stator. Motors including rotors having generally flat arrays of permanent magnetic poles and such stators which are spaced apart from and generally facing the permanent magnetic poles and have a plurality of magnetic windings, and pumps powered by such motors are included within the scope of the present invention.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to dynamo electric machines andstators for use in same. More particularly, the invention relates togenerally flat structured, dynamo electric machines, e.g., brushlesselectric motors, and to stators for use therein.

[0002] Brushless electric motors have been suggested and/or used forvarious purposes. In general, such motors come in at least twoconfigurations; a drum style motor in which the rotor and stator of themotor have generally cylindrical shapes; and a flat style motor in whichthe rotor and stator of the motor are present as generally flat discs.Although the drum style motors are often capable of generating morepower, the flat style motors have the advantage of being compact insize.

[0003] It would be advantageous to provide flat style or disc brushlesselectric motors which generate increased amounts of power.

[0004] Flat style brushless electric motors have been suggested for usewith impeller pumps. See, for example, Mizobuchi et al U.S. Pat. No.4,806,080; Kricker et al U.S. Pat. No. 5,332,374; and Atsumi U.S. Pat.No. 5,407,331. There continues to be a need to provide new impellerpumps driven by powerful flat style brushless electric pumps, inparticular for pumping liquids, such as water and the like.

SUMMARY OF THE INVENTION

[0005] New dynamo electric machines, stators for use in such machinesand pumps including such stators have been discovered. The presentinvention takes advantage of the discovery that dynamo electric machinestators comprising masses of metal particles, preferably pressed metalparticles, provide more efficient, powerful dynamo electric machines,preferably brushless electric motors having longer useful lives and/orproducing increased or enhanced amounts of power, relative to similarmachines having substantially the same dimensions and including statorsmade from solid metal members.

[0006] Without wishing to limit the invention to any particular theoryof operation, it is believed that the present stators which comprisemasses of metal particles are effective in disrupting, or otherwisemitigating against the harmful effects of, eddy currents that develop inthe stator. Such eddy currents reduce the effectiveness of the dynamoelectric machines, for example, the effective power generating abilityof the brushless electric motor. In any event, the present dynamoelectric machines, including stators comprising masses of metalparticles, have been found to be powerful and effective in manyapplications.

[0007] The present stators are useful in any dynamo electric machines,for example, motors, generators, alternators, motor/generatorcombinations, motor/tachometer combinations, frequency changers and thelike. Preferably the dynamo electric machine is of the brushless type,and more preferably of the brushless direct current (DC) type. The term“motor” is used extensively hereinafter and is meant to encompass orinclude within its scope any such dynamo electric machine.

[0008] One particularly useful application of such stators is inbrushless electric motors which power work components, such as pump andcompressor impellers, fan blades, mixing and blending implements and thelike. A very advantageous configuration provides such stators used incombination with rotors which are integral with the work component.Pumps, such as liquid handling pumps, powered by such brushless electricmotors are very beneficial embodiments of the apparatus of the presentinvention.

[0009] The present motors, stators, apparatus and pumps are relativelystraightforward in construction and easy to use. These motors, stators,apparatus and pumps provide a high degree of reliability and longeffective life and provide one or more advantages which enhanceperformance and/or cost effectiveness.

[0010] In one embodiment, the present invention is directed to motors(dynamo electric machines), preferably brushless electric motors, whichcomprise a rotor and a stator. The rotor has a rotary axis and includesa plurality of permanent magnetic poles arranged in a generally flatarray. The stator, which comprises a mass of metal particles, preferablya mass of pressed metal particles, is spaced apart from and generallyfacing the generally flat array of permanent magnetic poles. The statorhas a plurality of magnetic windings positioned and adapted to effectrotation of the rotor about the rotary axis upon energization thereof.

[0011] Reduced eddy currents preferably are obtained during operation ofsuch motors relative to the operation of similar motors in which thestator comprises a solid metal mass or member instead of the mass ofpressed metal particles. In addition, when compared to stator bodiesmade solely of polymeric materials, the present stator bodies providemotors with reduced effective air gaps between the stators and therotors, which feature ultimately yields more powerful motors relative tosimilar motors with stator bodies of polymeric materials. The presentstators preferably consist essentially of a mass of pressed metalparticles. The mass of pressed metal particles advantageously has adensity equal to at least about 95% of the theoretical density of asolid metal member. In a very useful embodiment, the stator includessubstantially linear acicular metal particles having a substantiallytriangular configuration.

[0012] The present motors preferably are brushless direct current (DC)electric motors, for example, brushless DC, one (1), two (2) or more,such as three (3), phase electric motors.

[0013] The present stators preferably comprise plates, for example,substantially flat plates, and a plurality of spaced apart projectionsor teeth including masses of metal particles, for example, as describedherein. The plates of the present stators have a first end surface, asubstantially opposing second end surface and a peripheral surfacetherebetween. The plurality of spaced apart projections extend from thesecond end surface away from the plate and, together with the second endsurface of the plate, define a plurality of slots therebetween.

[0014] The plate preferably has a central axis which intersects both thefirst end surface and the second end surface. Each of the plurality ofprojections preferably extends inwardly from the peripheral surface andterminates prior to intercepting the central axis.

[0015] Each slot of the plurality of slots preferably has asubstantially constant dimension between the two adjacent projectionswhich define the slot. In a very useful embodiment, the plate andprojections are unitary, that is are made of a single or unitary member.

[0016] Apparatus for performing useful work are provided which comprisework components, rotors and stators. The work components, such as pumpor compressor impellers, fan blades, mixing and blending implements,others assemblies which perform useful work on a material in contactwith the work component and the like, include a rotary axis and aremounted for rotation about the rotary axis. The work component isconfigured and positioned so that the rotation of the work component iseffective to perform work on a material in contact with the workcomponent. The rotor is coupled, preferably directly coupled, to androtatable with the work component and includes a plurality of permanentmagnetic poles arranged in a generally flat array. The stator is asdescribed previously and is adapted to effect rotation of the rotor andthe work component upon energization thereof.

[0017] As used herein, the term “directly coupled” as it relates to therelationship between the work component and the rotor refers to anapparatus in which the work component and the rotor are directly securedor attached to each other, so that no power transmission assembly, forexample, a shaft, gear arrangement or the like, transfers power from therotor to the work component. This “direct coupling” relationship, whichmay be considered an integral rotor/working component combination, veryeffectively provides power to the work component while reducing the sizeand space requirements of the apparatus.

[0018] In a very useful embodiment, the work component and stator arepresent in a unitary or single member, for example, a member made of asubstantially uniform composition.

[0019] Pumps are provided which comprise pump casings, impellers, rotorsand stators. The pump casing has an inlet and an outlet. The impellerhas a rotary axis and rotatably mounted within the pump casing forrotation about the rotary axis. The impeller is configured andpositioned relative to the pump casing so that rotation of the impelleris effective to urge fluid from the inlet to flow through the outlet.The rotor is coupled to and rotatable with the impeller and includes aplurality of permanent magnetic poles arranged in a generally flatarray. The stator is as described previously and is adapted to effectrotation of the rotor and the impeller upon energization thereof.

[0020] The present work apparatus and pumps preferably provide increasedor enhanced power, and more preferably reduced detrimental eddy currenteffects, during operation relative to similar apparatus and pumps inwhich a solid metal mass or member is used in place of the mass of metalparticles in the stator.

[0021] Each of the features disclosed herein is included within thescope of the present invention. In addition, all combinations of thepresently disclosed features which are not mutually inconsistent orincompatible are also included within the scope of the presentinvention.

[0022] These and other aspects and advantages of the present inventionare apparent in the following detailed description and claims,particularly when considered in conjunction with the accompanyingdrawings in which like parts bear like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a perspective drawing of a stator in accordance with thepresent invention.

[0024]FIG. 2 is a front plan view of the stator shown in FIG. 1.

[0025]FIG. 3 is a perspective drawing of an alternate embodiment of astator in accordance with the present invention.

[0026]FIG. 4 is a front plan view of the stator shown in FIG. 3.

[0027]FIG. 5 is a perspective view of a metal particle used in formingthe stators shown in FIGS. 1 to 4.

[0028]FIG. 6 is a perspective drawing of a fully assembled pump inaccordance with the present invention.

[0029]FIG. 7 is a perspective view of the pump shown in FIG. 6 with theparts exploded for illustrative clarity.

[0030]FIG. 8 is a cross-sectional view taken generally along line 8-8 ofFIG. 6.

[0031]FIG. 9 is a cross-sectional view taken generally along line 9-9 ofFIG. 8.

[0032]FIG. 10 is a front plan view of the rotor of the pump shown inFIG. 7.

[0033]FIG. 11 is an enlarged partial cross-sectional view of the centralarea of the pump shown in FIG. 6 emphasizing the space between thestator and rotor.

[0034]FIG. 12 is a cross-sectional view taken generally along line 12-12of FIG. 11.

[0035]FIG. 13A, 13B and 13C are front plan views of the stator of thepump shown in FIG. 7 illustrating a windings pattern for a six (6) pole,three (3) phase motor.

[0036]FIGS. 14A, 14B and 14C are front plan views of the stator shown inFIGS. 3 and 4 illustrating a windings pattern for a six (6) pole, three(3) phase motor.

[0037]FIG. 15 is a schematic illustration, side section, of an alternateembodiment of a motor in accordance with the present invention.

[0038]FIG. 16 is another schematic illustration, top view, of theembodiment shown in FIG. 15.

[0039]FIG. 17 is a schematic illustration, side section, of an furtherembodiment of a motor in accordance with the present invention.

[0040]FIG. 18 is another schematic illustration, top view, of theembodiment shown in FIG. 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0041] Referring now to the drawings, a stator, shown generally at 10,in accordance with the present invention includes a substantially flatplate 12 having a back surface 14, a substantially opposing frontsurface 16 and a peripheral surface 18 therebetween. Extending from thesubstantially flat front surface 16 and peripheral surface 18 are aseries of nine (9) projections which extend away from the front surfaceand radially inwardly from the peripheral surface and terminate prior tothe central axis 22 of the stator 10.

[0042] Each of the projections 20 includes a outer peripheral surface24, an inner peripheral surface 26 and two (2) equally sized sidesurfaces 28. The side surfaces 28 between adjacent projections 20,together with front surface 16, form a slot 30. Each of the slots 30 isequally sized and has a substantially constant dimension radiallyinwardly from the peripheral surface 12 and outer peripheral surface 24.A series of three (3) notches 32 are located on three (3) adjacentprojections 20 of stator 10. Each of these notches 32 is adapted toreceive and hold a Hall sensor. These Hall sensors are useful incontrolling the operation of the motor including stator Stator 10 isparticularly effective for use in a three (3) phase direct current (DC)brushless electric motor. However, stators similar in composition tostator 10 can be employed in one (1), two (2) or more phase DC brushlesselectric motors. Electric windings are provided in the slots 30. Onepattern for such windings is illustrated in FIGS. 13a, 13 b and 13 c.For the sake of clarity, only one winding is shown in each of FIGS. 13a,13 b and 13 c (and also in FIGS. 14a, 14 b and 14 c). However, arelatively large number of windings preferably are included in each ofthe slots 30, and the number of windings is chosen based on the desiredpower output of the motor.

[0043] An important feature of the present stator 10 is that it is madefrom a mass of metal particles. Specifically, stator 10 is made from amass of pressed metal particles. Such particles of metal, for example,metals having magnetic properties, i.e., metals which are attracted tomagnets, such as iron, nickel, cobalt, other magnetic metals and thelike, alloys, such as steel, iron and/or other metal or metals havingmagnetic properties alloyed with molybdenum, manganese, chromium,carbon, sulfur, silicone, copper, nickel, vanadium, niobium, gold,aluminum, phosphorus and the like and mixtures thereof, preferably aresubstantially linear, acicular particles having a substantiallytriangular configuration. Such a particle, shown generally at 34, isillustrated in FIG. 5.

[0044] Stator 10 may be, and preferably is, prepared in accordance withKrause et al U.S. Pat. 5,594,186, the disclosure of which isincorporated in its entirety herein by reference.

[0045] The metal particles 34 preferably have dimensions of about 0.002to about 0.05 inches in height (H dimension in FIG. 5), about 0.002 toabout 0.05 inches along the base (B dimension in FIG. 5) and about 0.006to about 0.20 inches in length (L dimension in FIG. 5). The metalparticles preferably have a substantially triangular cross-section and adie fill ratio of less than 3 to 1, with sufficient particle flowcharacteristics to permit the economic manufacture of the stator havinga density of at least about 95%, and more preferably at least about 96%,of the theoretical density of a solid metal member.

[0046] It should be noted that the metal particles which may be used toproduce the present stators can be of any suitable size, shape andconfiguration. Such particles preferably are of such configuration thata flat style motor, as described herein, including a stator made from amass of such particles provides for increased power production and/orreduced detrimental eddy current effects relative to a similar motor inwhich the stator is made from a mass of solid metal rather than the massof such particles. Also, the metal particles having a substantiallytriangular cross-section useful in the present invention are not limitedto the embodiment shown in FIG. 5. Such metal particles can havelongitudinal surfaces that are independently convex, concave and/orplanar.

[0047] In addition, the present stators can be made in the form of acomposite in which the mass of metal particles is combined, e.g.,layered, mixed or otherwise composited, with one or more othermaterials, for example, polymeric materials, wood and the like andmixtures thereof. Such a composite stator should include a sufficientamount of the metal particles to function effectively as a stator and toprovide at least one of the benefits or advantages described herein.Such composite stators can be produced using conventional compositeproduction techniques, for example, mixing, layering, compressing,shaping, injection molding, etc.

[0048] The stator 10 of the present invention may be prepared by thetraditional metal powder process comprising the steps of: (1) forming ametal particle mixture comprising the metal particles and a lubricant;(2) cold uniaxial pressing of the mixture to form a green compact havinga high green density and good green strength; (3) heating the greencompact at a sufficient temperature to pyrolyze the lubricant and formthe metal stator; (4) optionally sintering the stator at a sufficienttemperature for a sufficient time to impart additional strength to thestator and form a sintered stator; and (5) cooling the stator orsintered stator, then performing optional secondary operations on thestator to provide a finished metal component. Preferably, the methodcomprises a single cold, uniaxial pressing step, a single heating step,and a single sintering step, and provides a green compact and a statorhaving a density at least 95%, and preferably at least 96%, of thetheoretical density, and a finished stator of essentially the identicalsize and shape of the green compact.

[0049] The lubricant used is typically an organic compound having adensity of about 0.8 to about 1 g/cc (gram per cubic centimeter). Incontrast, the powdered metal typically has a density of about 6 to about8 g/cc. Accordingly, on a volume basis, even a small amount of lubricantby weight occupies an appreciable portion of the die volume. To achievea high density, the volume occupied by lubricant preferably isminimized. Therefore, the lubricant preferably is present in an amountof about 0.015% to about 0.4% and more preferably about 0.015% to about0.25%, by weight of the metal particle mixture.

[0050] The lubricant is an organic compound capable of being decomposed,or pyrolyzed, at the heating temperature. The pyrolysis products aregases which are expelled during heating. The lubricant may be a solid atroom temperature and incorporated into the metal particle mixture inparticulate form. Examples of lubricants include, but are not limitedto, ethylene bis-stearamide, C₁₂ to C₂₀ fatty acids, for example,stearic acid and the like, paraffins, synthetic and/or natural waxes,polyethylene, fatty diesters, fatty diamides and the like and mixturesthereof. Salts of organic acids, like zinc, lithium, nickel, iron,copper, and/or magnesium stearate, also can be used as the lubricant.However, acid salt lubricants can leave a metal oxide by-product in thefinished stator. The metal oxide by-product can adversely effect thestator.

[0051] For additional details regarding the production of stator 10 seethe above-noted Krause et al patent.

[0052]FIGS. 3 and 4 show a substantially similar stator, shown generallyat 40, which is substantially similar to stator 10. Components of stator40 which correspond to components of stator 10 are identified by thesame reference numeral increased by 30.

[0053] The primary difference between stator 40 and stator 10 is in thenumber and size of projections 50 relative to projections 20.Specifically, stator 40 has eighteen (18) projections 50 as opposed tonine (9) projections 20. Each of the projections 50 is substantiallysmaller in size than the projections 20.

[0054] Stator 40 can be employed in a three (3) phase electric motor inwhich electric windings are provided within the slots 60 of the stator,using a winding pattern as shown in FIGS. 14a, 14 b and 14 c. Of course,a stator structured similarly to stator 40 can be used in a one (1), two(2) or more phase DC brushless electric motor.

[0055] In the following description, the stator 10 is used. However, itshould be noted that stator 40 can be similarly used.

[0056] A motor/work component in accordance with the present inventionis illustrated as follows. A motor/pump combination, shown generally at110, includes a housing 112 which is made up of a pump cover 114, a pumpcase 116, a bulkhead housing element 118, a stator housing 120, acontrol housing 122 and a control cover 124. These housing components ofcombination 110 are fastened together using a plurality of conventionalscrew-type fasteners 126 which pass through each of the housingcomponents from pump cover 114 to control cover 124. Conventionalfastener nuts 127 are coupled to the fasteners 126 to maintain thefasteners in place.

[0057] Pump cover 114 includes a liquid inlet 130, while pump case 116includes a liquid outlet 132. An impeller 134, a rotor 136 and stator 10(including magnetic windings which are not shown) are positioned in theassembled combination 110, as shown in FIG. 8. The bulkhead housingelement 118 carries a bulkhead sheet 138 which includes a centrallylocated boss 140. The combination of bulkhead housing element 118 andbulkhead sheet 138 is an integrally formed structure and forms a staticseal which prevents the stator 10 from being exposed to the liquid beingpumped. Stator 10 is disposed in stator housing 120. Control housing 122houses the controls for the operation or activation of the stator 10.

[0058] As shown in FIG. 8, centrally located boss 140 is configured tosupport stationary axle 144, which is of tubular (hollow or solid)construction, at end 146. The boss 140 and/or end 146 of axle 144 arekeyed or include engaging flat surfaces which facilitate maintaining theaxle stationary relative to the boss. Axle 144 extends beyond thebulkhead sheet 138 into impeller 134 through the central opening 148 ofannular rotor 136.

[0059] Impeller 134 includes an opening 152 which extends away from theinlet 130 and is configured to allow both axle 144 and rotating bearing154 to be received therein. End 155 of axle 144 in opening 152 is free,that is it is not secured to impeller 134. In addition, a thrust bearing156 is positioned in the boss 140 and is maintained stationary. Thisthrust bearing 156 faces the back surface 158 (FIG. 8) of bearing 154which rotates with impeller 134 and rotor 136 around axle 144. Thrustbearing 156 can be relatively small because the net thrust force isreduced since the axial force from the rotor 136 opposes the forceinduced by pressure rise.

[0060] Annular rotor 136 includes a series of six (6) alternatingpermanent magnetic poles 159, as shown in FIG. 10. Permanent magneticpoles 159, which are alternating north (N) and south (S) magnetic poles,are arranged in a circular array and are positioned to face the stator10. In addition, rotor 136 includes an annular region 161 extending awayfrom stator 10 which has the magnetic properties of iron. Annular region161 is coextensive with the areas of permanent magnetic poles 159perpendicular to the rotary axis 170 of motor/pump combination 110.Region 161 with the magnetic properties of a soft magnetic material,such as iron, enhances the interaction between the stator 10 and rotor136, thereby enhancing the ability of the rotor 136 to be rotated inresponse to the magnetic windings located on stator 10 and enhancespower generation.

[0061] The rotor 136 can be made of individual magnetic segments toprovide the permanent magnetic poles and a region or layer(corresponding to region 161) of iron located on the back side (awayfrom stator 10) of the rotor to provide the magnetic properties of asoft magnetic material. One alternative is to use a ring magnet, inplace of the individual magnet segments, to provide the plurality ofpermanent magnetic poles, together with a back layer or region of ironand the like having magnetic properties of a soft magnetic material.However, rotor 136 preferably is an integral structure, for example,made of a composite of a thermoplastic polymeric matrix material, suchas polypropylene and the like, and strontium ferrite and the likeparticles , which can be magnetized to provide both the alternatingpermanent magnetic poles 159 as well as an annular region 161 extendingaway from the stator 10 which has the magnetic properties of a softmagnetic material.

[0062] In producing such a composite rotor, the percentage of eachconstituent is adjusted in order to obtain the desired balance ofmagnetic and structural properties. The composite rotor may be formed byan injection molding process in which the mixed constituents is heatedto be flowable and then forced into a closed cavity mold. While themixed material is still in the mold, magnetizing apparatus,appropriately positioned relative to the mold, is energized, therebyaligning the magnetic particles within the mixed material. In apreferred embodiment, rather than having flux lines that areperpendicular to the pole face as they pass through the rotor 136, theinternal flux at the back region (corresponding to region 161) of therotor is directed to turn parallel to the pole face surface and towardsthe adjacent opposite polarity poles. Essentially, this creates a fluxreturn path within the rotor 136 and eliminates the need for a separatemagnetic part (back iron).

[0063] The integrally structured rotor 136 described herein is anexample of a ring magnet with the additional feature that a region 161(FIG. 7) of the structure is magnetized to have magnetic properties of asoft magnetic material. Having such an integral structure providessubstantial benefits. For example, reduced weight is achieved whichreduces pump wear and vibration. Also, the use of an integral rotor 136reduces the number of parts included in the combination 110.

[0064] Impeller 134 includes a series of curved vanes 160 which arepresent in the primary liquid flow path between inlet 130 and outlet132. Upon rotation of impeller 134, vanes 160 are effective to impartcentrifugal energy to the liquid passing through inlet 130 which urgesthe liquid to flow under increased pressure through outlet 132. Thus,impeller 34 and vanes 60 provide the primary pumping action inmotor/pump combination 110.

[0065] The impeller 134 is directly coupled to, that is integral with,the rotor 136. Thus, impeller 134 rotates in direct response to therotation of rotor 136 with no coupling or power transfer assembly, suchas a shaft, gear arrangement and the like, between these two components.This direct coupling feature reduces the size of combination 110 and thenumber of components required. In a very useful embodiment, impeller 134and rotor 136 are present as a single or unitary member. For example, asingle part structured or configured to include both impeller 134 androtor 136, for example, made from the composite material describedpreviously with regard to rotor 136, can be formed using conventionaltechniques and performs very effectively in accordance with the presentinvention. Such a unitary impeller 134/rotor 136 is shown in thedrawings simply by considering the impeller and rotor as a single part.The advantages provided by such a unitary impeller (work component)134/rotor 136 include size reduction, reduced member of components andease of assembly.

[0066] The maximum magnetic cross-sectional area of rotor 136perpendicular to rotary axis 170 of the pump 110 is larger than themaximum cross-sectional area of impeller 134 perpendicular to the axis.The use of a relatively large rotor 136 allows much shorter housingprofiles, for example, relative to drum style brushless electricmotor/pump combinations. In addition, the relatively large rotor 136provides a larger area adjacent the bulkhead sheet 138 for dissipationof heat, for example, into the liquid from inlet 130 (as is describedhereinafter), thereby reducing or even eliminating the need for bypasscooling passages. Further, the large rotor 136 provides the extra areaneeded for the diffusion sections of the combination 110 so that thereis less wasted space. Moreover, the large rotor 136 relative to theimpeller 134 provides increased power to the impeller while, at the sametime, reducing the weight of the impeller relative to the rotor. Sincerelatively less weight is being rotated, the combination 110 performsmore efficiently. In other words, more of the power that is generated bythe interaction between the stator 10 and the rotor 136 is passed to theliquid being pumped through outlet 132.

[0067] The stator 10 includes a plurality of magnetic windings 172 (seeFIGS. 13A, 13B and 13C) positioned to interact with the permanentmagnetic poles 159 of the rotor 136 to effect rotation of the rotor andthe impeller 134 upon energization of the windings. The combination ofrotor 136, stator 10 (with windings 172) and controls in control housing122 forms a six (6) pole, three (3) phase brushless DC electric motorassembly. In this embodiment, the windings 172 on stator 10 can beprovided as illustrated in FIGS. 13A, 13B and 13C. Of course, thepresent invention is not limited to any specific number of permanentmagnetic poles or to a motor of any particular phase or phases. The discor flat arrangement of the present motors and motor/pump combinationallows substantial flexibility in terms of size, number of permanentmagnetic poles and motor configurations.

[0068] The controls included within control housing 122 act to controlthe operation of the stator 10 so as to provide the desired rotation ofthe rotor 136 and impeller 134. These controls can be based onelectronics which are conventional and well known in the art. Inparticular, controls which are useful in operating brushless DC electricmotors may be employed. Since such controls are conventional and wellknown in the art, a detailed description thereof is not needed topractice the present invention and is, therefore, not presented here.

[0069] An increase in efficiency is achieved by reducing the runningfriction of the motor/pump combination 110. This is accomplished, atleast in part, by using a portion of the liquid from inlet 130 toestablish a fluid film between the rotating rotor 136 and impeller 134and the stationary frame, that is the bulkhead sheet 138, stator 10 andassociated components. This fluid film is provided as follows.

[0070] With particular reference to FIGS. 11 and 12, a portion of theliquid from inlet 130 passes into a fluid passageway 173 in impeller134. Bearing 154 includes a series of four (4) fluid pathways 174 whichextend along the outer surface 176 of the axle 144 along the entirelength of the bearing 154. These fluid pathways 174 empty into the spacebetween the bulkhead sheet 138 and the back surface 178 of impeller 134.Further, back surface 178, as shown in FIG. 12, includes a series ofradially extending vanes 180 which are rotatable with the impeller 134and positioned to urge liquid from the fluid pathways 174 to flow intothe space 182 between the bulkhead sheet 138 and the impeller 134 androtor 136. This liquid forms a film which reduces friction between therotating and non-rotating components of motor/pump combination 110 andconducts heat caused by the rotation away from the site of the rotation,thereby facilitating more efficient operation of the combination. Theliquid is in fluid communication with the outlet 132 so that acontinuous flow of liquid is provided in the fluid pathways 174 and inthe space 182 between the impeller 134 and rotor 136 and the bulkheadsheet 138.

[0071] Bulkhead housing element 118 and bulkhead sheet 138 provide aseal between the rotating portion, e.g., rotor 136 and impeller 134, ofcombination 110 and the non-rotating or stationary portion, e.g., stator10, of the pump. Thus, no rotating member passes through the seal platedefined by bulkhead housing element 118 and bulkhead sheet 138. Thereare no moving parts within the stationary or electromagnetic portion,e.g. stator 10, of the combination 110. All the moving parts have beenintegrated into the rotating portion of combination 110. This integratedrotor design feature reduces wear and tear on pump 110 and avoidsexposing the stator 10 to the liquid being pumped.

[0072] Bulkhead sheet 138 which is positioned, has a configurationand/or is made of material so as to provide one or more enhancements tomotor/pump combination 110. Thus, bulkhead sheet 138 is positionedbetween the rotor 136 and the stator 10 and includes one or moreregions, particularly regions which directly face the rotor, which arein contact with and structurally supported by the stator. Allowing thestator 10 to structurally support at least a portion of the bulkheadsheet 138 reduces the size of combination 110, and allows the use of arelatively thin film or layer of material as the bulkhead sheet. Forexample, the region or regions of the bulkhead sheet 138 which arestructurally supported by the stator 10 are preferably less than about30 mils thick. Having the bulkhead sheet 138 very thin allows forincreased interaction between the windings 172 on the stator 10 and thepermanent magnetic poles 159 on the rotor 136. This provides forincreased efficiency in the interaction between the stator 10 and rotor136 and increased power generation.

[0073] Moreover, the bulkhead sheet 138, particularly the regions of thebulkhead sheet which directly face the rotor 136, are preferably made ofa material having a low magnetic permeability, to further reduce thedetrimental effects of eddy currents. The reduced magnetic permeabilityof bulkhead sheet 138 allows for increased interaction between thewindings 172 on the stator 10 and the magnetic poles 159 on the rotor136. The high coefficient of thermal conductivity allows foradvantageously increased dissipation of heat and, ultimately, increasedlife of motor/pump combination 110.

[0074] Because at least a portion of the bulkhead sheet 138 isstructurally supported by the stator 10, a wide range of materials,satisfying both the reduced magnetic permeability and increasedcoefficient of thermal conductivity requirements, noted above, can beused in producing the bulkhead sheet. In other words, since the bulkheadsheet 138 is at least partially structurally supported by the stator 10,the strength of the material from which the bulkhead sheet is made isnot a primary concern. Examples of useful materials for the bulkheadsheet 138 are brass, austenitic stainless steel, polymeric materials andthe like.

[0075] Motor/pump combination 110 is constructed so that a veryeffective static seal is provided by bulkhead sheet 138 so that noliquid from inlet 130 comes in contact with the stationary portion,e.g., stator 10, of the pump. The fact that a static seal, rather than arotating or otherwise moving seal, is used reduces wear and tear andincreases the effective useful life of pump 110.

[0076] Components of housing 112 and impeller 134 can be produced usingpolymeric materials.

[0077] In another embodiment, shown schematically in FIGS. 15 and 16, abrushless DC electric motor, shown generally at 200, includes two (2)stators 210 and a rotor 236 therebetween. The rotor 236 is secured tomotor shaft 202. The flux goes between stators 210 as shown in FIG. 16.Motor 200 may be considered to be a stacked motor in that a plurality ofstators 210 are used in rotating rotor 236 and motor shaft 202.Increased power is provided by such a stacking arrangement. Such acombination of a single rotor and two (2) stators can be used as thebasic building block of a larger, more highly stacked motor.

[0078]FIGS. 17 and 18 illustrate one such more highly stacked motor 300,which is made up of two (2) pair of stators 310. Two (2) rotors 336,each of which is located between the stators 310 of a different pair ofstators, are provided. Both of the rotors 336 are attached to shaft 302.

[0079] Each of the stators 210 and 310 has substantially the sameconfiguration as stator 10, previously described. Also, each of therotors 236 and 336 has substantially the same configuration as the rotor136, previously described, except that rotors 231 include no region(corresponding to region 161) with the magnetic properties of a softmagnetic material.

[0080] Each pair of stators 310 of motor 300 is independent of the otherstator pair. The flux can either go through the back to back stators 310of motor 300 or can be directed within each pair of stators 310, asshown in FIG. 18.

[0081] The stacked motors 200 and 300 can be used in any application inwhich the rotation of motor shaft 202 and 302, respectively, is to betranslated into useful work. Stacked motors 200 and 300 can becontrolled using conventional control electronics, shown schematicallyat 204 and 304, respectively. Control electronics 204 and 304communicate with each of the stators 210 and 310, respectively, toenergize the windings located on each of these stators. Energizing thewindings on stators 210 and 310 causes the rotors 236 and 336,respectively, and motor shafts 202 and 302, respectively, to rotate. Theother end of each of the motor shafts 202 and 302 may be secured to animplement, such as a pump, compressor, fan and the like, which isoperated by the power transmitted by the shaft.

[0082] The present stators, and dynamo electric machines and pumpsincluding such stators, provide substantial benefits whether a singlestator and rotor are employed or a plurality of stators and/or rotorsare employed. These stators, which include a mass of pressed metalparticles, preferably provide for enhanced power generation, forexample, relative to a similar dynamo electric machine employing astator including a solid metal mass or member in place of a mass ofpressed metal particles. Such enhanced power generation can result inreduced machine size and/or increased overall power generation so thatthe dynamo electric machines including such stators advantageously canbe used in a broader range of applications including heavy duty or powerintensive applications. The present stators represent a substantialimprovement relative to conventional stators, particularly because ofthe enhanced power generating capabilities of dynamo electric machinesincluding such stators as well as the relatively straightforward andcost effective way in which such stators can be produced.

[0083] While this invention has been described with respect to variousspecific examples and embodiments, it is to be understood that theinvention is not limited thereto and that it can be variously practicedwithin the scope of the following claims.

What is claimed is:
 1. A dynamo electric machine comprising: a rotorhaving a rotary axis, and including a plurality of permanent magneticpoles arranged in a generally flat array; and a stator spaced apart fromand generally facing said generally flat array and having a plurality ofmagnetic windings positioned and adapted to effect rotation of saidrotor about said rotary axis upon energization thereof, said statorcomprising a mass of metal particles.
 2. The dynamo electric machine ofclaim 1 which is a brushless direct current electric motor
 3. The dynamoelectric machine of claim 1 wherein reduced eddy current effects areobtained during operation of said motor relative to the operation of asimilar dynamo electric machine in which a solid metal mass is used inplace of the mass of metal particles.
 4. The dynamo electric machine ofclaim 1 wherein said stator comprises a mass of pressed metal particles.5. The dynamo electric machine of claim 4 wherein said mass of metalparticles has a density equal to at least about 95% of the theoreticaldensity of a solid metal mass.
 6. The dynamo electric machine of claim 1wherein said stator includes substantially linear, acicular metalparticles having a substantially triangular configuration.
 7. The dynamoelectric machine of claim 1 which is a three phase, brushless directcurrent electric motor.
 8. The dynamo electric machine of claim 1 whichfurther comprises a work component coupled to and rotatable with saidrotor.
 9. The dynamo electric machine of claim 1 which comprises aplurality of said stators.
 10. A stator for use in a dynamo electricmachine comprising: a plate configured to be substantially flat andhaving a first end surface, a substantially opposing second end surfaceand a peripheral surface therebetween; and a plurality of spaced apartprojections extending from said second end surface away from said plateand defining a plurality of slots therebetween, said plate and saidprojections comprising a mass of metal particles.
 11. The stator ofclaim 10 wherein said plate has a central axis which intersects bothsaid first end surface and said second end surface, and said pluralityof projections each extend inwardly from said peripheral surface andterminate prior to intersecting said central axis.
 12. The stator ofclaim 11 wherein each slot of said plurality of slots has asubstantially constant dimension between the two projections whichdefine the slot.
 13. The stator of claim 10 wherein said plate and saidprojections are unitary and comprise a mass of pressed metal particles.14. The stator of claim 10 wherein said mass of pressed metal particleshas a density equal to at least about 95% of the theoretical density ofa solid metal mass.
 15. The stator of claim 10 which includessubstantially linear, acicular metal particles having a substantiallytriangular configuration.
 16. An apparatus for performing useful workcomprising: a work component having a rotary axis and being mounted forrotation about said rotary axis, said work component being configuredand positioned so that the rotation of said work component is effectiveto perform work on a material in contact with said work component; arotor coupled to and rotatable with said work component, and including aplurality of permanent magnetic poles arranged in a generally flatarray; and a stator spaced apart from and generally facing saidgenerally flat array and having a plurality of magnetic windingspositioned and adapted to effect rotation of said rotor and said workcomponent upon energization thereof, said stator comprising a mass ofmetal particles.
 17. The apparatus of claim 16 wherein reduced eddycurrent effects are obtained during operation relative to the operationof a similar apparatus in which a solid metal mass is used in place ofthe mass of metal particles in the stator.
 18. The apparatus of claim 16which comprises a plurality of said stators.
 19. The apparatus of claim18 which comprises a plurality of said rotors.
 20. The apparatus ofclaim 16 wherein said stator comprises a mass of pressed metalparticles.
 21. The apparatus of claim 20 wherein said mass of pressedmetal particles has a density equal to at least about 95% of thetheoretical density of a solid metal mass.
 22. The apparatus of claim 16wherein said stator includes substantially linear, acicular metalparticles having a substantially triangular configuration.
 23. A pumpcomprising: a pump casing having an inlet and an outlet; an impellerhaving a rotary axis and being rotatably mounted within said pump casingfor rotation about said rotary axis, said impeller being configured andpositioned relative to said pump casing so that the rotation of saidimpeller is effective to urge fluid from said inlet to flow through saidoutlet; a rotor coupled to and rotatable with said impeller, andincluding a plurality of permanent magnetic poles arranged in agenerally flat array; and a stator spaced apart from and generallyfacing said generally flat array and having a plurality of magneticwindings positioned and adapted to effect rotation of said rotor andsaid impeller upon energization thereof, said stator comprising a massof metal particles.
 24. The pump of claim 23 wherein reduced eddycurrent effects are obtained during operation relative to the operationof a similar pump in which a solid metal mass is used in place of themass of metal particles in the stator.
 25. The pump of claim 23 whichcomprises a plurality of said stators.
 26. The pump of claim 23 whichcomprises a plurality of said rotors.
 27. The pump of claim 23 whereinsaid stator comprises a mass of pressed metal particles.
 28. The pump ofclaim 27 wherein said mass of metal particles has a density equal to atleast about 95% of the theoretical density of a solid metal mass. 29.The pump of claim 23 wherein said stator includes substantially linear,acicular metal particles having a substantially triangularconfiguration.